ANCHORAGE, Alaska — A small fisheries technology firm armed with computers and hydrophones is trying to locate and silence the dinner bell that attracts pods of killer whales to longline vessels fishing in the Bering Sea.

“The problem is the killer whales are eating turbot and black cod right off the line,” said Pat Simpson of Scientific Fishery Systems Inc., whose staff has been studying the orcas under a $50,000 grant from the Alaska Fisheries Development Foundation.

“It is not clear what is attracting them or how they are locating the longliners,” he said. “The problem is we’re conditioning a generation of whales to subsist off of longline fisheries.”

Orcas are eating the fish before the fish can be harvested. After 10 months of research, Simpson and his staff think the culprit could be the longline itself, acting as an underwater transducer, telling the whales the fish are there, ready to eat.

All it takes then is for one orca to alert the rest of the pod, and three dozen or so toothy orcas, weighing 8,000 to 12,000 pounds apiece, converge on the longline and gobble up the catch before it can be pulled on board.

Full-grown orcas eat about 550 pounds of food a day.

“We have not yet found the acoustic sounds — the dinner bell — that we can correlate with the whale activity,” Simpson said. “It is a work in progress. If we can locate that sound or series of sounds, the next effort would be to eliminate that attraction. It is one of our more interesting projects.”

The bulk of data analysis is being handled by Alex Kulinchenko, a SciFish employee who designed and tested the data collection systems, and Parisa Nahavandi, an intern who is studying for a degree in engineering at the University of California, San Diego.

“We are trying to find any collaboration between fishing activities and the presence of the orcas,” Kulinchenko said.

To that end, Kulinchenko designed the system for recording the sounds of the whales in the area of freezer processors and also around buoys marking the longlines in the Bering Sea.

The acoustics equipment was installed on the bow and on deck of the longline ship Prowler while it was in dry dock in Oregon in June. Prowler owner John Winther fishes for black cod and turbot in the Bering Sea.

“At one point, the Prowler had 10 killer whales eating fish off the longline,” Simpson said. “We noticed you would find one whale would locate the boat. We would hear some vocalizations and other whales would appear. When there were several whales in the area, they would vocalize more. One of the whales would locate the boat and call the other whales over.”

“We think they come when the ships come to get the fish,” Kulinchenko said. “It’s almost like they are waiting for the bell.”

Kulinchenko and Nahavandi note that orcas apparently are not attracted to fish hooked on the lines beneath the buoys until fishermen attempt to pull the harvest into the vessel.

The longliners fish in very deep water, 800 to 900 feet, so it is simply easier for the orcas, who can dive to about 100 feet, to wait for harvesters to bring the fish to them, they said.

They hypothesize that the tension in the fishing line is causing low frequency vibrations which travel quickly through the water, alerting the scout for a pod of killer whales. When they pull up the line there is a very clear humming sound, Nahavandi said.

“At the beginning, I listened to every single sound file,” said Nahavandi, who half jokingly talks of learning to speak whale.

“I got used to listening to different sounds. I listened for certain whale sounds, their whistles and clicks.”

The longlines being pulled onto the decks of the processor “sound like the plucking of a very large guitar string,” she said.

Since orcas appear to prey on certain longliners, one of the next steps would be collection and analysis of more acoustical data, comparing acoustics of vessels attracting orcas with those that do not. Researchers also need to acquire additional acoustic data at deeper depths to decrease boat equipment noise recorded, they said.

SciFish will make its recommendations to the Alaska Fisheries Development Foundation on Nov. 11, Simpson said. If further research shows that the acoustics of the vessels themselves are attracting the orcas, the problem might be resolved with a bubble mask under the vessel, Simpson said.

If, on the other hand, vibrations from certain longlines are ringing the dinner bell, “we would have to get more clever at confusing them,” Simpson said.

The use of a bubble cloud, injecting air through small holes down the keel of a ship, is a technique used to quiet the passage of military vessels. While sound doesn’t penetrate through the bubbles, the production of the bubbles themselves makes sound, so there is no free lunch, Simpson said.